The most common and most likely answer to this crossword clue is the 5 letter word TURPS
I've seen this crossword clue in The Guardian
T
U
R
P
S
More clues leading to the result TURPS
- Thinner sheep carrying fatter rump
- Amazingly, Trump’s giving away millions, getting thinner!
- Thinner rams making way for their leader
- Initially tubby uncle, rather podgy, slightly thinner
- Thug raps occasionally with singular spirit
- Tottenham’s underachieving Rafa produced scoring headers showing spirit
- Ejected half-naked from disturbances — that’s Aussie booze!
- Stuff leading tradesmen use removing paint stains
Buddy explains!

The straight part
We know that "Thinner" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case thinner = turps.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does TURPS mean?
TURPS noun- Turpentine or turpentine substitute.
- Any alcoholic drink.